1. Field of Invention
The invention relates to a reset system, and particularly relates to a micro-controller reset system and reset method thereof.
2. Description of Related Art
A reset system is commonly found in a current electrical apparatus to perform a reset process to ensure that the process is performed normally when power is applied to the electrical apparatus again. For example, when power starts to be applied to the electrical apparatus, the reset system output is used to hold a micro-controller in the electrical apparatus at a reset state for a period of time so as to perform a reset process. Conventionally, a timer is disposed in the reset system to accomplish this reset task. The timer continues to hold the micro-controller at the reset state for a preset period of time, and after the preset period of time enables the micro-controller to leave the reset state and to begin operation.
The conventional reset system is operated before the electrical apparatus is booted. However, some micro-controllers also need to perform a rest process before the electrical apparatus is shut down to ensure that the process is performed normally when power is applied to the electrical apparatus again. Therefore, there is a need for a reset system to automatically perform a rest process before the electrical apparatus is shut down.
Accordingly, the present invention provides a reset system and reset method to make a micro-controller of an electrical apparatus perform a reset process while the electrical apparatus is turned off.
The invention provides a micro-controller reset system. The reset system comprises an enable circuit, a buck converter and a reset circuit. The enable circuit electrically connects to a system power source. When a voltage of the system power source is raised to be greater than a first voltage, the enable circuit outputs an enable signal with a steep leading edge. The buck converter converts the system power source to output a micro-controller power source to the micro-controller according to the enable signal. The reset circuit electrically connects to the system power source and the micro-controller power source. When a voltage of the system power source is dropped to be smaller than a second voltage, the reset circuit outputs a reset signal to reset the micro-controller. The first voltage is smaller than the second voltage. When the reset system enters a power drop state, the voltage of the system power source begins to drop to cause the voltage of the micro-controller power source to drop. When the voltage of the system power source is dropped to be smaller than the second voltage but greater than the first voltage, the reset circuit outputs the reset signal and the enable circuit still outputs the enable signal. Because the enable signal controls the buck converter to output the micro-controller power source to the micro-controller, the micro-controller continues to work to receive the reset signal to perform a reset process. Therefore, the micro-controller may perform a reset process while the micro-controller is in a power drop state.
In an embodiment, the reset circuit further comprises a first transistor and a voltage comparator. The first transistor electrically connects to the micro-controller. The voltage comparator electrically connects to the first transistor. When the voltage of the system power source is dropped to be smaller than the second voltage, the voltage comparator outputs a positive voltage signal to turn on the first transistor. When the first transistor is turned on, the first transistor outputs a reset signal to reset the micro-controller.
In an embodiment, a positive input end of the voltage comparator electrically connects to a divided voltage of the micro-controller power source, and a negative input end of the voltage comparator electrically connects to a divided voltage of system power source. When a voltage at the positive input end is smaller than that at the negative input end, the voltage comparator outputs a negative voltage signal to turn off the first transistor.
In an embodiment, the reset circuit further comprises a resistor. One end of the resistor electrically connects to the positive input end of the voltage comparator, the other end of the resistor electrically connects to the output end of the voltage comparator. The resistor improves the positive feedback velocity of the voltage comparator.
In an embodiment, the enable circuit further comprises a second transistor and a third transistor. The second transistor electrically connects to the system power source. The third transistor electrically connects to the second transistor, the system power source and the buck converter. When the voltage of the system power source is raised to be greater than the first voltage, the second transistor is turned on and the third transistor is turned off to make the enable circuit output the enable signal.
In an embodiment, when the voltage of the system power source is smaller than a third voltage, both the second transistor and the third transistor are turned off. The enable signal is from the divided voltage of the system power source. When the voltage of the system power source is raised to be greater than the third voltage but smaller than the first voltage, the third transistor is turned on. The enable signal is 0 volt. When the voltage of the system power source is raised to be greater than the first voltage, the second transistor is turned on and the third transistor is turned off. An efficient enable signal is outputted.
In an embodiment, the enable circuit further comprises a delay circuit electrically connected to the second transistor and the system power source to delay the second transistor to be turned on.
The invention also provides a micro-controller reset method. First, when a voltage of a system power source is raised to be greater than a first voltage, an enable circuit is triggered to output an enable signal with a steep leading edge. Then, according to the enable signal, a buck converter is triggered to convert the system power source to output a micro-controller power source to a micro-controller. Finally, When a voltage of the system power source is dropped to be smaller than a second voltage but greater than the first voltage, a reset circuit is triggered to output a reset signal to reset the micro-controller, and the enable circuit still outputs the enable signal to control the buck converter to output the micro-controller power source to the micro-controller to make the micro-controller in a work state to finish the reset process.
In an embodiment, the reset circuit further comprises a first transistor and a voltage comparator. The first transistor electrically connects to the micro-controller. The voltage comparator electrically connects to the first transistor. When the voltage of the system power source is dropped to be smaller than the second voltage, the voltage comparator outputs a positive voltage signal to turn on the first transistor. When the first transistor is turned on, the first transistor outputs a reset signal to reset the micro-controller.
In an embodiment, the enable circuit further comprises a second transistor and a third transistor. The second transistor electrically connects to the system power source. The third transistor electrically connects to the second transistor, the system power source and the buck converter. When the voltage of the system power source is raised to be greater than the first voltage, the second transistor is turned on and the third transistor is turned off to make the enable circuit output the enable signal.
Accordingly, when the electrical apparatus is turned off and the voltage of the system power source is dropped to be smaller than a special voltage, the reset circuit outputs a reset signal, and the enable circuit keeps outputting the enable signal to make the micro-controller at a work state to finish the reset process. Therefore, the micro-controller may perform a reset process according to the reset signal.
It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed.